A typical configuration of semiconductor ionization radiation detectors and detector arrays is such that the incoming radiation passes an entrance electrode and interacts with the detector volume. The direction of the detected radiation is usually parallel or close to parallel to the electrical field lines within the volume of the detector (e.g., perpendicular to the detector electrodes). The electric field in the detector volume is created by a bias voltage applied to the detector electrodes.
There are also examples where detectors are specifically configured with electrodes parallel to incoming radiation and the direction of incoming photons is perpendicular to electric field lines within the detector. One such example is an edge-on configuration for either a single pixel or a linear array.